1. The Field of the Invention
The present invention relates to POP rivets. More particularly, the present invention relates to POP rivets used in the assembly of cash boxes and other secure enclosures. Most particularly, the present invention relates to a POP rivet assembly which cannot be tampered with without leaving traces of that tampering.
2. The Prior Art
Pop riveting represents a cheap and effective way of assembling light sheet fabrications. A POP rivet is inserted through a pair of aligned holes in an abutting pair of metal sheets and deformed to hold the sheets together. Pop riveting is particularly attractive in those situations where spot welding is impractical either because of low volume of production, precluding the expenditure required upon jigs and special welding heads; or because of inaccessibility of welding heads to the point of attachment. Further, spot welding can cause unwanted fusion between parts which are not to be welded.
Light steel boxes are commonly used as banknote cassettes in autotellers money to bank customers after normal banking hours upon presentation to the autoteller of a valid card by a customer. The autotellers operate over weekends and public holidays when banking staff are not in attendance. It is the custom, therefore, to provide for a third party, such as a security firm, to load the autoteller with fresh supplies of banknotes whenever required. The bank notes are provided in a cassette, pre-loaded in the bank and presented to the security firm for later loading. The cassette generally holds up to one hundred thousand dollars and is fabricated from mild steel including locks and other security devices. Pop rivet construction for such a box would be desirable, but is generally precluded because of the vulnerability of POP rivets to undetectable removal and replacement. The POP rivets can be drilled out, the box opened, some of the contents removed, and the POP rivet replaced. An undetectable opening of the box is thus accomplished and it cannot be proved at what stage the money which is missing has gone missing. The non-availability of POP riveting as a method for assembling cash boxes for autotellers has meant that this low production item has previously been fabricated in more expensive ways more suitable to high volume production.
It is, therefore, desirable to provide a POP rivet assembly which cannot be tampered with without leaving signs of that tampering. This would bring POP riveting into the same class of security as other methods of construction.